1. Technical Field
This invention relates to asynchronous electronic circuits, in particular, to asynchronous electronic circuits with memory arrays.
2. Background Information
An asynchronous circuit operates to define a particular state defined in terms of the input values to the circuit and in conjunction with the internal actions of the circuit. The asynchronous circuit may be a time domain or a sequence domain type of circuit. The asynchronous circuit may assert a specific signal at the specific occurrence of an event and for a specific duration. Two of the advantages of using asynchronous circuits include power conservation and the lack of a requirement for clock alignment between various stages, thus alleviating the need for global synchronization.
Generally speaking, the greatest power consumption by an asynchronous circuit occurs when the circuit is transitioning from one state to another. A synchronous circuit utilizes a clock cycle, thus the circuit will consume more power because of the continual cycling of circuits, especially during refresh cycles or clock-initiated transitions. In the asynchronous circuit, the greatest power consumption will occur during those transition stages when the circuit changes states. Ideally, the asynchronous circuit will consume less power than the same synchronous circuit. Since clocking circuitry is not used in asynchronous circuits, the elimination of the clock circuit provides a further power savings. This makes the asynchronous circuit ideal for applications where the conservation of battery power is important. Further, the circuit is deemed to be self-timing.
However, asynchronous circuits have been difficult to apply in memory applications, where a clock cycle provides the timing for writing or reading data in memory in a sequential process. Therefore, a need to provide a memory circuit that is capable of holding its state without refreshing the memory cells, but yet providing the timing for a sequential writing or reading of data to a memory cell in an allotted time slot is required. This becomes more complicated where the temperature of the devices may vary or the operating environment of the devices is severe allowing for rapid changes in temperature or where a multitude of devices acting in concert have different operating environments. As one example, downhole telemetry systems used for monitoring and/or controlling oil and gas exploration tools can see extreme temperature variation across the system.